Method for the production of alkalimetal salts of triorgano-silanols



MM June 14, 1949 METHOD FOB THE PRODUCTION OF ALKALI- MEI'AL SALTS OFIBIOBGANO-SMNOLS James Franklin Hyde, Corning. N. Y., alsignor to GlassWorks, Corning. N. 2.. a corporation of New York No Drawing. ApplicationNovember 25, 1946, Serial No. 712.040

3 Claims. 1

The present invention relates to the preparation of certainorganosilicon salts.

Organosilicon materials in which the manic radicals are linked tosilicon by carbon to silicon bonds have been described in theliterature. Compounds of this type are known which have from one to fourorganic radicals linked to the silicon. Triorganosilanes have beendescribed in which the remaining valence of the silicon is satisfled byvarious groups such as chloride, hydroxy and ethoxy.

Objects of the present invention are to provide particulartriorsanosilanes in which the remaining valence of the silicon issatisfied by oxygen which in turn is linked to alkali metal, and methodsfor their produ tion.

Compositions prepared in accordance with the present invention are ofthe type RR'aSiOM in which R represents methyl, R represents methyl orphenyl and M represents an alkali metal.

In accordance with the present invention, a triorgano alkoxy silane orproducts such as are derived from the hydrolysis and condensationthereof are reacted with an alkali metal oxide in the presence 01 waterby eliminating the water from the system. It has been found that underthese conditions the reactants, which normally do not produce thecompounds here desired, will interact with the production of the desiredcom- Positions.

The compounds produced in accordance herewith are of rather uniquecharacter. While these compounds are readily hydrolyzed by water, cropsof crystalline material may be obtained during the removal of waterwhich contain water of crystallization. In addition to crystallizingwith water of crystallization, crystalline complexes are in some casesformed with alcohol and with alkali metal hydroxide.

In conducting the process of the present invention, the alkali metaloxide, which is employed, may be either free of water. in which casewater is added to the system, or it may contain somewaterasinthecaseofcommercialalkalimetal oxide. Such water is present aswater of composition in alkali metal hydroxide which is present in theoxide. The alkali metal oxide and water may be added in the form ofalkali metal hydroxide. when the hydroxide is employed. it is preferredto limit the amount of water present to not more than suilicient to forma concentrated solution, inasmuch as further dilution will merelyincrease the amount oi water to be removed and may result in a decreasedyield.

The organosilicon material employed for proto vent.

2 duetion of these salts is in general an ester of an organosilanehaving the desired organo radicals linked to the silicon, or materialssuch as are produced by the condensation of the hydrolyzate thereof.These condensates are the hexaorganodisiloxanes. When the esters areemployed directly, it is preferred to employ the esters of the loweraliphatic alcohols, whereby the alcohol produced upon interaction withthe alkali metal hydroxide is liberated. and may be removed bydistillation. The ethoxy esters are satisfactory for this purpose,though they frequently result in the salt produced being discoloredsomewhat by side] condensation products. By employing the methoxyesters, this discoloration is avoided.

The alkali metal oxide, the organosilicon material which contains thegroup RR'aSi-, and the water. which together constitute the reactionmixture are heated to effect the interaction. This interaction proceedsas the water is removed by distillation. During the course of thedistillation, salt containing water of crystallization frequentlycrystallizes from the mixture. Upon removal of the hydrated salt and thewater the anhydrous salt remains, and may be crystallized or otherwisepurified. In this connection, it is to be noted that various oi. thesalts particularly the salts of trimethyl silanol may be sublimed.

It is preferred to have an excess of the creamsilicon material presentduring reaction. This promotes the formation of the simple salt. Aparticularly desirable manner of operation involves heating a mixture ofalkali metal hydroxide and water, and continually adding the disiloxane.In this operation the temperature is preferably maintained at aboveabout C. The water is liberated as the salt is formed.

If desired an excess of alkali metal oxide may be employed. This mayresult in the formation of a complex with alkali metal hydroxide, whichcomplex may be separated from the simple salt. It may then be interactedwith the hexaorganodisiloxane to give the alkali metal salt of thetriorganosilanol.

In order to increase the rate 0! the reaction, it is preferred to add alower aliphatic alcohol of boiling point below water. In order to removethe alcohol and water, and to facilitate purification of the product, anorganic solvent which has a boiling point at least about that of watermay be added. After distillation of the water and alcohol, and afterremoval oi any complex salt which may have crystallized, the desiredsalt in anhydrous state may be recovered from the sol- Buitable solventsfor this purpose are tel 3 uene, xylene, heptane and petroleum etherboiling above water. Also petroleum ether boiling point from 90 to 100C. may be employed, in which case the distillate is condensed, thepetroleum ether separated from the alcohol and water and returned to thereaction mixture.

In the case of the potassium salt of trimethyl silanol, when the amountof water in the system is limited to less than one mol oi water per mol.of alkali, the water present will crystallize with a portion of the saltas the hydrate. Removal of the water in this way results in theremainder of the salt in solution being anhydrous.

The hydrates, i. e. salts containing water of crystallization, which areat times produced as crops oi crystals during the distillation are verysoluble in the conventional organic solvents. The anhydrous salts whichare obtained are highly hydroscopic and are slightly less soluble in theorganic solvents. The hydrates may be dehydrated at atmospherictemperature or at slightly elevated temperature but below the meltingpoint of the hydrate by subjecting the salts to a high vacuum in thepresence of a dehydrating agent.

The utility of the salts of this invention as catalysts tor thepolymerization of cyclic diorganosiloxanes is shown in the copendingapplication Serial Number 766,460, iiled August 5, 1947, now Patent2,453,092.

Ezample 1.-l6.2 parts by weight of hexamethyldisiloxane were mixed with6.2 parts 0i sodium oxide and 17 parts of methyl alcohol This mixturewas distilled. A residue of 14.35 parts by weight of insoluble materialwas obtained. parts by weight of hexamethyldi siloxane and 1.8 parts byweight of water were added to the residue. The water was in amountsufficient to convert the sodium oxide to sodium hydroxide. 13.5 partsof methyl alcohol were added gradually with boiling under reflux untilsolution was complete. On cooling the characteristic needle crystals ofthe complex of the salt and alcohol crystallized. These crystals had aneutralization equivalent of 176.5. Theory for (CH3)3SiONa'2CH3OH is176. Petroleum ether having a boiling range of 90 to 100 C. was addedand the mixture was heated to boiling for a short time. Amicro-crystalline precipitate was formed which had a neutralizationequivalent of 79.5. Theory for (CI-maSiONa-NaOI-I is 81. The flitratewas evaporated to a solid crystalline residue. This residue had aneutralization equivalent of 114.5. Theory for (CHJ)3SlON8 is 112. Thissalt gives the following X-ray diffraction pattern:

Example 2.59 parts by weight of trimethylethoxysilane were mixed with21.6 parts of powdered sodium hydroxide, which had an assay of 92.7%NaOH, and 0.8 part of methyl alcohol. The mixture was refluxed for 24hours. 11.8 parts of trimethylethoxysilane were then added and refluxingwas continued for an additional 18 hours. The reaction mixture was thenevapo' rated under high vacuum for 3 hours. The solid mass was extractedwith boiling petroleum ether. The extract was evaporated to dryness,heated under vacuum to free the hydrated salt of water, and the simplesalt so obtained was purified by sublimation at 130 to 140 C. under highvacuum.

The neutralization equivalent of the product was 113.

Emmple 3.-A mixture oi 32.4 parts by weight of hexamethyldisiloxane,26.9 parts of potassium hydroxide which contained 16.7% water and 1.6parts of methyl alcohol was prepared and allowed to stand at roomtemperature for 12 hours. It was then heated to a temperature Just belowboiling for 24 hours. The slight loss in weight which had occurred wasmade up by the addition of 3 parts of hexamethyldisiloxane. Refluxingwas continued an additional 8 hours. A further 6.5 parts ofhexamethyldisiloxane was added and refluxing was continued. The reactionmixture was then extracted in a Soxhlet with diethyl ether. The extractwas evaporated to dryness and placed under a high vacuum. Theneutralization equivalent of the salt so obtained was 124.1. Theory for.(Cl-blzSiOK is 128. The portion of the re action product which wasinsoluble in diethyl ether had a neutralization equivalent of 78.2 andwas the complex (CHa)aSiOK-2KOH.

Eccmple 4.-A mixture of 27.95 parts of hexamethyldisiloxane was refluxedwith potassium hydroxide which had a neutralization equivalent of 61.6.Ai'ter 10 days excess hexamethyldisiloxane was decanted and the residueextracted with diethyl ether to remove the hydrate. The residue was thesimple anhydrous salt and had a neutralization equivalent of 126. TheX-ray diil'raction pattern for the salt produced in Examples 3 and 4 isas follows:

Example 5.A mixture of 28.6 parts by Weight of symmetricaldiphenyltetramethyldisiloxane and 8 parts of sodium hydroxide wasprepared and heated to 225 to 230 C. Methyl alcohol was gradually addedduring the heating until the alkali had dispersed. This required 24parts of methyl alcohol. The mixture was heated under vacuum at to C. toremove water and alcohol. The reaction mixture was dissolved in a 50-50mixture of toluene and methyl alcohol. Upon evaporation, crystallizationoccurred, the precipitate being a complex of the desired salt. Thesolution was then placed under high vacuum and slowly heated to atemperature of 225 C. to remove residual disiloxane. The crude salt soobtained was recrystallized from petroleum ether having boiling rangefrom 30 to 60 C. The needle crystals so obtained had a melting point of87 to 94 C. and a neutral equivalent of 1765. Theory for CoH5(CHa)2SlONuis 174.

Example 6.A mixture was prepared of 12.3 parts by weight of symmetricaldimethyltetraphenyldisiloxane and 1.86 parts of sodium oxide whichcontained a small amount of water. The mixture was heated at to C. andsufiicient methyl alcohol was added to disperse the alkali, the amountbeing between 4 and 8 parts. The reaction mixture was heated undervacuum to remove methanol and water. A viscous reaction product wasthereby obtained which was largely dissolved on boiling with 12 to 16parts of toluene. The insoluble complex with sodium hydroxide wasremoved by filtering. The toluene solution was evaporated to asemi-solid mass. This mass was the remainder being water.

tion equivalent of the product so obtained was i 238. Theory for theanhydrous salt is 236. The

anhydrous salt may if desired be recrystallized readily from petroleumether.

Example 7.A mixture of parts by weight of sodium hydroxide and 60.5parts by weight of methyldiphenylethoxysilane was heated to 150 to 160C. The mixture was allowed to stand for 12 hours at 25 C. It was thenheated to 50 to 60 C. for 6 hours with intermittent application orvacuum. The mixture was then heated at 125 to 150 C. for 20 minutes andthe mixture allowed to stand at 50 to 60 C. for 12 hours. The reactionmixture was dissolved in a mixture of benzene and toluene, refluxed foran hour and filtered hot whereby the complex of the salt with sodiumhydroxide was separated. Petroleum ether of 90 to 100 C. boiling rangewas added and the benzene removed by evaporation. The monohydrate of thesodium salt of methyldiphenylsilanol was recovered by concentration ofthe solution. The hydrate was dehydrated over phosphorous pentoxide at140 C. The salt was recrystallized from petroleum ether.

Example 8.--Sixty parts of methyldiphenylethoxysilane was mixed with 17parts of potassium hydroxide having an assay of 83.3% KOH, The mixturewas heated for hour and then allowed to stand at 25 whereupon themixture became nearly solid. The mixture was then warmed under vacuumfor a short time to remove alcohol in the water, and then placed underhigh vacuum for 18 hours. The salt so obtained was dissolved in boilingtoluene and filtered to remove the complex of the salt and potassiumhydroxide. The filtrate was crystallized and yielded the monohydrate ofthe potassium salt of methyldiphenylsilanol. This salt was dehydratedfor 3 hours at 140 C. over phosphorous pentoxide. A product was obtainedwhich had a neutral equivalent of 251. Theory for CH3(C6H5)2S1OK is252.4. This salt may be recrystallized from xylene or petroleum ether.

Iclaim:

1. The method for the production of organosilicon compositions whichcomprises dehydrating a reaction mixture of an alkali metal oxide.water, and an organosilicon compound selected from the group consistingof compounds of the type RR'aSlY and (RR/:81) :0 where R representsmethyl, Y represents alkoxy and R is selected from the group consistingof methyl and phenyl radicals, whereby a salt is obtained of the generalformula RR'aSlOM in which R represents methyl, R is selected from thegroup consisting of methyl and phenyl radicals and M represents analkali metal.

2. The method in accordance with claim 1 in which the reaction mixtureis dehydrated by distillation.

3. The method for the production of organesilicon compositions whichcomprises dehydrating a reaction mixture of an alkali metal oxide,water, a lower aliphatic alcohol soluble in water, a hydrocarbon solventhaving a boiling point at least about that oi water and an organosiliconcomposition selected from the group consisting of compounds of the typeRR'aSiY and (RR'aSiizO where R represents methyl, Y represents alkoxyand R is selected from the group consisting of methyl and phenylradicals, effecting the dehydration by distillation whereby the alcoholand water are removed and whereby a solution of a salt is obtainedhaving the general formula RR'iSiOM in which R represents methyl, R isselected from the group consisting of phenyl and methyl radicals and Mrepresents an alkali metal.

JAMES FRANIUJIN HYDE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Volnov: "Journal Gen. Chem," U.S. s. R. 1940), vol. 10, pages 1600-1604.

Sauer: Journal Amer. Chem. Soc., vol. 66 (1944) pages 1707-1710,

